The present invention relates to a device for adsorptive drying compressed gas in an adsorber and regenerating the desiccant contained therein in a continuous operation.
Adsorbers of this type are known to comprise a first chamber and a second chamber, both of which containing the desiccant for adsorptive gas drying. One of the chambers is always connected to the gas flow from the compressor to the consumer while the other undergoes a regenerating phase of the desiccant.
This is accomplished by a first pneumatic changeover valve which connects the inlet of either the first chamber or the second chamber to the mains conveying the gas to be dried, and by a second pneumatic changeover valve which connects the outlet of either the first chamber or the second chamber to the mains through which the dry gas flows to the consumer.
Further, there is provided a choke joint interconnecting the outlet sides of the first and second chamber. The inlet side of each chamber is provided with a solenoid relief valve.
These elements, in combination with a timing mechanism for controlling the solenoid valves, permit a continuous drying and regenerating operation in cycles in such a way that always one chamber is engaged in gas drying while, at the same time, the desiccant in the other chamber is regenerated. During this operation, reversal of the pneumatically operated changeover valves is tripped, utilizing control pulses transmitted from the timing mechanism, closing the relief valve of the chamber being in the regenerating cycle and opening the relief valve of the chamber being in the drying cycle.
In a known device of this type cycle reversal is accomplished in such a manner that the timing mechanism, once the preset operating time has elapsed, causes the closing of the relief valve of the unpressurized regenrating chamber, so as to enable a working pressure to build up above the choke joint. Thereafter, the relief valve of the drying chamber (under working pressure) opens, so as to admit pressure release in this latter chamber.
Inversion of the pressure conditions on both sides of the changeover valves obtained in this manner ensures that the valves are automatically pressed into their reverse operating positions.
The timing mechanism is set to an operating cycle just sufficient to provide drying of the max. gas volume with the max. rate of flow or resp. output from the consumption circuit, for which the desiccant charge is rated. Accordingly the choke joint is designed to be capable of branching off a partial dry gas flow sufficient to regenerate the moisture-laden (and saturated) desiccant within the preset cycle. This means that in a practically applicable case the working cycle is 5 minutes and the partial flow is 0.15 of the max. rate of flow at a prevailing working pressure of 7 bar.
Devices of this type have, however, the following disadvantage: Occurence of the max. rate of flow is quite rare in practice. The actual rates of gas flow during the fixedly preset cycle are essentially lower and, as a matter of fact, vary between 30% and 70% of the max. rate of flow. This means likewise that the desiccant is loaded to an accordingly less substantial extent. On the other hand, the dry gas flow branched off for regenerating, the volume of which depending on the fixed outlet of the choke and on the constant working pressure prevailing in the drying chamber, has always the constant value ##EQU1## wherein p represents the working gauge pressure in bar. Consequently only a fractional part of the branched off gas flow is utilized regularly for regeneration. The result is a comparatively high loss of gas and thus a waste of expensive energy.
It is, therefore, the object of the invention to adapt the regenerating gas flow R to the actually consumed volume of gas Q and thus to achieve savings in energy cost.